This method allows for the determination of water sorption in a laboratory setting and provides a measure for how the durability is impacted as a result of immersion in water. Post-immersion durability reduction is calculated as the difference between the durability of the as-received sample and the durability of the wetted product. A post-immersion durability reduction of 0 means there was no change to the durability of the thermally treated pelletized fuel as a result of wetting, whereas a post-immersion durability reduction of 3 indicate that the durability dropped by three percentage points as a result of wetting.